The topological susceptibility in finite temperature QCD and axion cosmology

We study the topological susceptibility in 2+1 flavor QCD above the chiral crossover transition temperature using Highly Improved Staggered Quark action and several lattice spacings, corresponding to temporal extent of the lattice, $N_\tau=6,8,10$ and $12$. We observe very distinct temperature dependences of the topological susceptibility in the ranges above and below $250$ MeV. While for temperatures above $250$ MeV, the dependence is found to be consistent with dilute instanton gas approximation, at lower temperatures the fall-off of topological susceptibility is milder. We discuss the consequence of our results for cosmology wherein we estimate the bounds on the axion decay constant and the oscillation temperature if indeed the QCD axion is a possible dark matter candidate.Comment: 19 pages and 7 figures; v2: A new figure, a few references and minor comments added; published versio

Free energy for parameterized Polyakov loops in SU(2) and SU(3) lattice gauge theory

We present a study of the free energy of parameterized Polyakov loops P in SU(2) and SU(3) lattice gauge theory as a function of the parameters that characterize P. We explore temperatures below and above the deconfinement transition, and for our highest temperatures T > 5 T_c we compare the free energy to perturbative results.Comment: Minor changes. Final version to appear in JHE

Local Polyakov loop domains and their fractality

Schadler H-P, Endrödi G, Gattringer C. Local Polyakov loop domains and their fractality. In: Proceedings of 31st International Symposium on Lattice Field Theory LATTICE 2013 — PoS(LATTICE 2013). Trieste, Italy: Sissa Medialab; 2014: 134

Fractality and other properties of center domains at finite temperature: SU(3) lattice gauge theory

Endrödi G, Gattringer C, Schadler H-P. Fractality and other properties of center domains at finite temperature: SU(3) lattice gauge theory. Physical Review D. 2014;89(5): 054509.Using finite temperature SU(3) lattice gauge theory in the fixed scale approach we analyze center properties of the local Polyakov loop L(x). We construct spatial clusters of points x where the phase of L(x) is near the same center element and study their properties as a function of temperature. We find that below the deconfinement transition the clusters form objects with a fractal dimension D<3. As the temperature is increased, the largest cluster starts to percolate and its dimensionality approaches D=3. The fractal structure of the clusters in the transition region may have implications regarding both the small shear viscosity and the large opacity of the quark gluon plasma observed in heavy-ion collision experiments